An awful lot of people have been telling lies under oath at the Disclosures Tribunal. That’s according to the chairman of the inquiry, Judge Peter Charleton.

The tribunal has heard from numerous gardaí, a dozen or so personnel in the child protection area, journalists and even lawyers. All are engaged in work in which the truth is regarded as central to their work. Yet, it would appear that the judge is of the opinion that some among them have lied under oath, which, if proved, would constitute a criminal offence.

“I need to know that you’re telling the truth,” he told witness Debbie McCann, a reporter for the Mail On Sunday.

“I’m not an idiot. I’ve sat here for nearly 90 days and I know that an awful lot of people haven’t told me the truth.”

The statement will not come as a surprise to anyone closely following the inquiry, but that the chairman felt moved to express it publicly spoke volumes.

The intervention was one of a number of a similar character that he made yesterday. Soon after noon, he issued what could be interpreted as a warning to tell the truth and nothing but.

“It has occurred to me forcibly and it is necessary for me to say that the statement you made to the tribunal was one that carries consequences if it is not correct,” he said, referencing an earlier statement that Ms McCann had made.

“There is an obligation on citizens to tell the full truth.”

After that he rose for lunch to give the witness and everybody else something to chew on.

Ms McCann has emerged as a major witness in an inquiry into whether the former head of the Garda press office, Superintendent Dave Taylor, conducted a smear campaign, as he has alleged, under orders from former commissioner Martin Callinan.

Yesterday she said that she had never been briefed negatively about Sgt McCabe by any member of An Garda Siochana. Her father was a retired superintendent in 2014. She also repeatedly claimed journalistic privilege on conversations she had with Supt Taylor even though he has waived his privilege.

“I really wish I could help you further on this,” she said at one point. “It would make my life easier but I have a career as a journalist.”

After further exchanges, the chairman had this to say: “Sometimes it may be the case that people claim privilege as an illegitimate shield.”

In February 2014 McCann went to the home of Miss D, the woman who made a claim of inappropriate touching against Sgt McCabe in 2006, dating from eight years later.

Miss D’s father was a colleague of McCabe’s who had been disciplined earlier in 2006 after being reported by Sgt McCabe.

Miss D’s allegation was dismissed completely by the gardaí, the state solicitor and the DPP following an investigation.

Supt Taylor has claimed that historic allegation was used to smear Sgt McCabe.

Ms McCann’s colleague, Alison O’Reilly, has told the tribunal that Ms McCann claimed the woman was in a bad way and that she had been told about her story by Supt Taylor and Nóirín O’Sullivan. Ms McCann denies this.

Ms McCann travelled to Cavan to Miss D’s house, but the girl’s mother sent her away. A few days later another journalist, Eavan Murray, also travelled to Cavan to attempt to interview Miss D.

According to Supt Taylor, both spoke to him before travelling. If his version was accepted it would infer that he was, as he has claimed, orchestrating a smear campaign.

Supt Taylor gave the tribunal a list of reporters he claimed to have briefed negatively about Sgt McCabe. Debbie McCann was not on the list, even though he later admitted that he had a conversation with her before she went to Cavan.

He also said he would have encouraged her to travel, inferring any contact with the D family would paint Sgt McCabe in a bad light.

Yesterday afternoon, it was put to MS McCann by Alison O’Reillly’s lawyer that she was ill-disposed towards Sgt McCabe.

“You had a strong position on the credibility or otherwise of Maurice McCabe and it was against McCabe?” Ms McCann denied this.

A few weeks after these two reporters attempted to get an interview in Cavan, crime reporter Paul Williams succeeded in doing so. A series of articles were printed in the Irish Independent as a result, suggesting the original allegation was much more serious than it was, and that Miss D was claiming there was a cover-up. Both of these claims have been shown in the tribunal to have no foundation.

The chairman will have to determine what all this adds up to and whether it goes towards the claim of a smear campaign.

Already, the tribunal has been told by a number of high profile witnesses that Martin Callinan had told them Sgt McCabe was a child abuser. Mr Callinan denies all of these claims.

Towards the end of Ms McCann’s direct evidence, Judge Charleton once more emphasised what was at stake as far as he is concerned.

“I think that truth is the most important value that exists in life,” he said. How close the chairman manages to get to it before writing his report remains to be seen.